The present invention relates to single straight tube flowmeters, which are also known as Coriolis type flowmeters, and also to methods of operating of such flowmeters.
Flowmeters of this type are known in the art, such as for example the flowmeter PROMAX of Endress-Hauser Corporation, OPTIMASS 7000 of KPOHNE Flesstechnik GmbH & Co.KG, MICRO-MOTION Series T. etc. The common problem of such flowmeters is their dependency from exterior nonelectrical disturbances, such as vibrations of pipelines, alternating loads in flange connections of the device with the pipelines, and also loads caused by temperature differences of the pipe and the body.
In the known flowmeters steps are taken to deal with these problems. The presence of compression and stretching forces on the pipe which change its rigidity are taken into consideration by measurements of temperature in several points of the pipe and the body and providing corrections for changes to the flow rate and density by calculations in the electronic block. In addition, by selection of a material of the pipe and the body, a temperate range is increased. For example MICRO MOTION Corporation uses titanium that has high corrosion resistance and low thermal expansion coefficient.
Several approaches are used to deal with vibration disturbances to increase accuracy of flow rate and density measurements in single straight tube flowmeters. The tubes can be equilized by a mass which oscillates in a counter phase and with which the windings of the adapters and excitation unit are connected. It allows to bring its characteristics closer to the characteristics of two-tubes flowmeters. However when the density in the tube changes, the equilibrium is partially distorted, and also measures are taken to stabilize of a plane of tube oscillations by increasing the rigidity of the tube in a plane, that is perpendicular to the oscillation plane. This is provided by a configuration of partitions located near fixing points of the tube and fixedly connected with the body, by a construction of the equilizing device, by an additional body arranged inside an outer body on flexible pipelines with the flowmeter located inside of the additional body to unload it from an exterior vibrations.
These methods and means for fighting with vibration distuirbances are passive protection methods, that allow to reduce influence of vibration on the operation of the flowmeter, but cannot exclude it completely, since they can not adapt it to a value, direction and character of vibration.